Method for slope improvement

ABSTRACT

A method for slope improvement including layering a life-extending layer on the surface of a protective layer made from mortar or concrete sprayed onto a slope in order to prevent rain water or the like from entering cracks in the protective layer, inhibit degradation of the protective layer, and prevent mortar pieces or concrete pieces from spalling off the protective layer, the method for slope improvement being characterized in that the life-extending layer is formed by a coating layer that has a crack conformability of 0.8 mm or larger and has salt-blocking properties and neutralization-preventing properties.

TECHNICAL FIELD

The present invention relates to a method for slope face improvement,which prevents penetration of rainwater and the like from cracks thatform in a protective layer comprising mortar or concrete sprayed onto aslope face, restricts degradation such as salt damage or neutralizationof the protective layer, and also prevents detachment of the protectivelayer.

This application claims priority on the basis of Japanese PatentApplication 2014-138999 filed in Japan on Jul. 4, 2014 the content ofwhich is cited herein.

PRIOR ART

Mortar or concrete (also referred to below as “mortar etc.”) is sprayedonto cliff faces and slope faces which have degraded due to weatheringand the like, in order to protect the cliff face or the slope face andto prevent instability of the faces, and a protective layer comprisingmortar or concrete is provided on said faces (e.g., see Patent Document1). Forms of cliff face or slope face instability which may be citedinclude slides caused by erosion, surface-layer crumbling, and collapse.A protective layer comprising mortar etc. is provided in order toprevent this kind of instability from occurring. The construction methodinvolving providing this kind of protective layer is one of the methodsmost often used because not only does it provide a strong blockingeffect with respect to weather, temperature changes and seepage water,it also has excellent properties in terms of construction

PRIOR ART DOCUMENT Patent Document

-   Patent Document 1: JP 2013-1585 A

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

In this regard, Japan has a large number of cliff faces and slope faces,and in recent years there have not only been collapses of slope facesand oblique faces as a result of frequent intensive rainfall and naturaldisasters, there has also been loss of human life. The collapse of slopefaces etc. impedes rescuing people and disaster relief. One cause of thecollapse of slope faces etc. that may be cited is due to the fact thatrainwater etc. penetrates into cracks formed as a result of degradationover time of the protective layer comprising mortar etc. sprayed ontosaid slope faces etc., and the rainwater erodes the rear surface of theprotective layer. As a result, cavities are formed between thefoundation and the protective layer, and this may lead to crumbling ofthe protective layer.

Examples of the causes of degradation of the protective layer comprisingmortar etc. which may be cited include: (1) penetration of rainwaterfrom cracks produced by degradation over time; (2) frost damage; and (3)chemical erosion (salt damage (calcium chloride) and neutralization(carbon dioxide) etc.).

When the protective layer degrades, adhesion between the protectivelayer and the foundation (slope face) is lost over time to produce afloating state, and this causes a phenomenon in which cracks are furtherenlarged as the foundation becomes looser. Furthermore, degradation ofthe protective layer over time is also caused by a phenomenon in whichvegetation enters surface-layer areas of the protective layer wheresedimentation has occurred, and this pushes the cracks wider apart.

Frost damage to the protective layer is a phenomenon in which free waterin the protective layer comprising mortar etc. and moisture in theaggregate which has high water absorption are repeatedly subjected to afreezing and thawing action, whereby cracks are formed in the protectivelayer, the surface layer portion of the protective layer peels, andbreakage occurs from the area close to the surface, causing gradualdegradation.

Salt damage in the protective layer constitutes the followingphenomenon. During the winter period, snow-melting agents such ascalcium chloride are scattered on road surfaces in mountainous regionsin order to prevent freezing of roads due to snow. When a motor vehicleor the like travels on a road surface on which a snow-melting agent hasbeen scattered and when the wind blows, the snow-melting agent isdispersed and may adhere to the protective layer formed on a cliff faceor a slope face. When the snow-melting agent adheres to the protectivelayer, steel material in the protective layer corrodes and cracks formfrom inside the protective layer due to volume expansion, so the mortaretc. becomes detached. The mortar etc. is likely to degrade in this waybecause of the snow-melting agents, and therefore the protective layerhas a short lifespan in mountainous regions and the mortar etc. has tobe frequently sprayed, which increases the cost entailed in stabilizingcliff faces and slope faces.

Neutralization of the protective layer is a phenomenon in which carbondioxide (CO₂) in the atmosphere penetrates into the mortar etc., causinga carbonation reaction which reduces the pH of the mortar etc. which isessentially alkaline. When neutralization progresses from the surface ofthe protective layer and reaches the steel material present within theprotective layer, this damages the passivation film. As a result, thesteel material corrodes and cracks are formed in the protective layerdue to volume expansion of the corroded material formed, and theprotective layer becomes detached.

The present invention has been devised in light of the situationdescribed above, and the aim thereof lies in providing a method forslope face improvement which prevents penetration of rainwater and thelike from cracks that form in a protective layer comprising mortar orconcrete sprayed onto a slope face, restricts degradation such as saltdamage or neutralization of the protective layer, and also preventsdetachment of the protective layer caused by the degradation.

Means for Solving the Problem

A method for slope face improvement according to one mode of the presentinvention (referred to below as “the method for slope face improvementaccording to the invention of this application”) is a method in which alifespan-extending layer is layered on a surface of a protective layercomprising mortar or concrete sprayed on a slope face, wherebypenetration of rainwater etc. from cracks that form in the protectivelayer is prevented, degradation of the protective layer is restricted,and detachment of mortar pieces or concrete pieces from the protectivelayer is prevented, said method being characterized in that a coatinglayer having crack-following properties of 0.8 mm or greater,salt-blocking properties and neutralization-preventing properties isformed as the lifespan-extending layer.

According to the method for slope face improvement of the presentinvention, the coating layer preferably comprises a polymer compound.

According to the method for slope face improvement of the presentinvention, a primer layer is preferably formed between the protectivelayer and the lifespan-extending layer.

According to the method for slope face improvement of the presentinvention, a topcoat layer is preferably formed on thelifespan-extending layer.

According to the method for slope face improvement of the presentinvention, the polymer compound is preferably at least one selected fromthe group consisting of: polyurethane resin, polyurea resin, epoxy resinand acrylic resin.

Advantage of the Invention

According to the present invention, a coating layer havingcrack-following properties of 0.8 mm or greater, salt-blockingproperties and neutralization-preventing properties is formed as alifespan-extending layer on the surface of a protective layer comprisingmortar or concrete sprayed on a slope face, and as a result, it ispossible to prevent penetration of rainwater and the like from cracksthat form in the protective layer, restrict degradation such as saltdamage or neutralization of the protective layer, and also preventdetachment of the protective layer caused by the degradation; it is thuspossible to envision a longer lifespan for the protective layer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating the method for slope faceimprovement according to a mode of embodiment, and shows a cross sectionparallel to the height direction of terrain having a cliff face or aslope face;

FIG. 2 is a schematic diagram illustrating the method for slope faceimprovement according to a mode of embodiment, shows a cross sectionparallel to the height direction of terrain having a cliff face or aslope face, and is an enlargement of part of FIG. 1; and

FIG. 3 is a front view illustrating an example of the method for slopeface improvement according to a mode of embodiment, in which visualguidance serving as a safety measure is provided by a topcoat layer.

MODE OF EMBODIMENT OF THE INVENTION

A mode of embodiment of the method for slope face improvement accordingto the present invention will be described.

It should be noted that this mode of embodiment is specificallydescribed in order to provide a better understanding of the essentialpoint of the present invention and does not limit the present inventionunless particularly indicated otherwise.

FIG. 1 is a schematic diagram illustrating the method for slope faceimprovement according to this mode of embodiment, and shows a crosssection parallel to the height direction of terrain having a slope face.FIG. 2 is a schematic diagram illustrating the method for slope faceimprovement according to this mode of embodiment, shows a cross sectionparallel to the height direction of terrain having a slope face, and isan enlargement of part of FIG. 1.

In FIG. 1 and FIG. 2, the reference symbol 1 denotes a foundation, 1 adenotes a slope face (cliff face), 2 denotes a protective layercomprising mortar or concrete; 3 denotes a lifespan-extending layer; 4denotes a primer layer; and 5 denotes a topcoat layer. It should benoted that the primer layer 4 and the topcoat layer 5 may be used asrequired.

The method for slope face improvement according to this mode ofembodiment is a method in which the lifespan-extending layer 3 islayered on a surface 2 a of the protective layer 2 comprising mortaretc. sprayed on the slope face 1 a of the foundation 1, wherebypenetration of rainwater etc. from cracks that form in the protectivelayer 2 is prevented, degradation of the protective layer 2 isrestricted, and detachment of mortar pieces or concrete pieces from theprotective layer 2 is prevented, a coating layer having crack-followingproperties of 0.8 mm or greater, salt-blocking properties andneutralization-preventing properties being formed as thelifespan-extending layer 3.

The lifespan-extending layer 3 sustains and reinforces the protectivelayer 2 and thereby extends the lifespan (useful life) thereof (prolongsthe life thereof).

The protective layer 2 is a layer comprising conventional mortar orconcrete which is sprayed in order to protect the slope face 1 a of thefoundation 1 and to prevent the slope face 1 a from become unstable.

It should be noted that the slope face 1 a may equally be a cliff facewhen the foundation 1 is a cliff.

The coating layer forming the lifespan-extending layer 3 hascrack-following properties of 0.8 mm or greater, as defined in StructureConstruction Management (July 2015 edition, 3-6: Concrete, 3-6-2:Surface Protection Requirement Performance, Nippon Expressway ResearchInstitute Company Limited), and preferably 5 mm or greater, morepreferably between 1 mm and 10 mm.

If the crack-following properties have a value of less than 0.8 mm, thecrack-following properties of the coating layer with respect to changescaused by degradation over time of the protective layer 2 comprisingmortar etc. are inadequate, and it is not possible to obtain an adequateeffect in terms of the lifespan of the protective layer 2 afforded bythe lifespan-extending layer 3.

The coating layer forming the lifespan-extending layer has salt-blockingproperties of no greater than 3.7×10⁻⁵ mg/cm²·day, as defined in the“Quality Standard Test Method JHS 417-1999 for Concrete CoatingMaterials” of Structure Construction Management of the Japan HighwayPublic Corporation, and the coating layer has excellent salt-blockingproperties if the defined value satisfies no greater than 5.0×10⁻³mg/cm²·day. That is to say, the coating layer which is a reinforcinglayer 3 has a considerable effect in terms of blocking salts such ascalcium chloride used as a snow-melting agent, and can prevent corrosionof the protective layer 2 caused by said salts.

The coating layer forming the lifespan-extending layer 3 is such thatthe neutralization-preventing properties defined in StructureConstruction Management (July 2015 edition, 3-6: Concrete, 3-6-2:Surface Protection Requirement Performance, Nippon Expressway ResearchInstitute Company Limited), are 1 mm or less in terms of neutralizationdepth.

The thickness of the lifespan-extending layer 3 is preferably 1 mm to 2mm.

If the thickness of the lifespan-extending layer 3 is within this range,it is possible to achieve salt-blocking properties in thelifespan-extending layer 3 of no greater than 3.7×10⁻⁵ mg/cm²·day.

The coating layer forming the lifespan-extending layer 3 preferablycomprises a polymer compound able to satisfy the abovementionedcrack-following properties, salt-blocking properties andneutralization-preventing properties.

Furthermore, the polymer compound is preferably at least one selectedfrom the group consisting of: acrylic resin, epoxy resin, polyesterresin, polyurethane resin, polyurea resin, acrylic urethane resin,asphalt urethane resin and asphalt.

These polymer compounds may be used alone or two or more types may bemixed for use.

For example, when a slope face 1 facing a road is constructed, apreferred polymer material which may be used is an ultra-fast-curingpolyurethane resin or polyurea resin etc. which constitutes a materialthat cures rapidly, in order to shorten construction time and lift lanerestrictions on a road caused by one-way traffic.

The lifespan-extending layer 3 is constructed over a large surface areawith respect to the slope face 1 a of the foundation 1, and therefore itis necessary to form the lifespan-extending layer 3 efficiently. Thecuring time after spraying of mortar etc. is between 4 and 28 days, soit is difficult to shorten the construction time. In contrast to this,ultra-fast-curing polyurethane resin or polyurea resin has a curing timeafter coating of 1 day, and therefore it is possible to shorten theconstruction time. It is therefore possible to efficiently construct thelifespan-extending layer 3 on the slope face 1 a of the foundation 1 byusing an ultra-fast-curing polyurethane resin or polyurea resin.

There is no particular limitation as to the method for applying thecoating layer that forms the lifespan-extending layer 3 on the surface 2a of the protective layer 2 or on a surface (referred to below as “thesurface”) 4 a on the opposite side to the face of the primer layer 4 incontact with the protective layer 2, but according to an exemplarymethod which may be cited, a coating composition comprising a polymercompound that forms the coating layer is applied to the surface 2 a ofthe protective layer 2 or to the surface 4 a of the primer layer 4 bymeans of a two-liquid impact agitation/mixing-type spray gun or a staticmixer-type spray gun. In particular, when an ultra-fast-curingpolyurethane resin is applied by means of a spray gun, the coating filmmay be formed by supplying to the spray gun a curable mixture obtainedby mixing an isocyanate component and a polyol component, and applyingthis to the surface 2 a of the protective layer or the surface 4 a ofthe primer layer 4, or the isocyanate component and the polyol componentmay be separately supplied to the spray gun, and a mixture obtained bymixing of said components inside the spray gun may be applied to thesurface 2 a of the protective layer 2 or to the surface 4 a of theprimer layer 4 in order to form the coating layer.

The primer layer 4 preferably has affinity with the lifespan-extendinglayer 3 and the protective layer 2 comprising mortar etc., and there mayalso be cases in which the surface 2 a of the protective layer 2 iswhetted, so said primer layer is preferably able to bond to a wetsurface. Specific examples of primers forming the primer layer 4 whichmay be advantageously used include primers comprising epoxy resin orurethane resin which cures at normal temperature, and these primers maybe single-liquid curable primers or two-liquid curable primers.

Furthermore, the primer layer 4 may be omitted if there is adequatebonding between the protective layer 2 and the lifespan-extending layer3.

The topcoat layer 5 is formed with the aim of protecting thelifespan-extending layer 3 (improving the weatherability thereof),harmonizing with the landscape and providing visual guidance serving asa safety measure. Examples of the polymer compound forming the topcoatlayer 5 which may be used include a two-liquid curable solvent-basedacrylic urethane resin, a two-liquid curable aqueous acrylic urethaneresin, an aqueous acrylic resin, and an organo-siloxane resin.

The topcoat layer 5 is normally formed with the aim of protecting thelifespan-extending layer 3, but as shown in FIG. 3, it may equally beprovided as a different-colored region 6 having a different color fromthe lifespan-extending layer 3, on the opposite surface (referred tobelow as “the surface”) 3 a to the surface of the lifespan-extendinglayer 3 facing the protective layer 2. As shown in FIG. 3, thedifferent-colored region 6 is depicted as an arrow or the like forvisual guidance indicating the direction of travel on a road (seeFIG. 1) running along the slope face 1 a. There is no particularlimitation as to the shape, size (area) or number of different-coloredregions 6, and these may be suitably adjusted in accordance with theinformation (travel direction or warning about a slope failure, orlandslide etc.) represented by said different-colored regions 6.

Furthermore, when the different-colored region 6 is formed, a mixture inwhich a colored pigment commensurate with the aim is mixed with thepolymer compound forming the topcoat layer 5 may be used, and saidmixture may be applied to the surface 3 a of the lifespan-extendinglayer 3 as a distinct color from the lifespan-extending layer 3 in orderto form the different-colored region 6.

There is no particular limitation as to the method for coating thepolymer compound forming the topcoat layer 5 on the surface 3 a of thelifespan-extending layer 3, but examples of methods which may be citedinclude applying the polymer compound to the surface 3 a of thelifespan-extending layer 3 by means of a roller, a brush or a spray gunet cetera.

According to the method for slope face improvement of this mode ofembodiment, dirt and foreign material adhering to the surface 2 a of theprotective layer 2 comprising mortar etc. are first of all completelyremoved. Furthermore, if there are protrusions or differences in leveletc. on the surface 2 a of the protective layer 2, said surface 2 a ispreferably smoothed by making combined use of power tools and manualtools.

In addition, after the whole of the region of the surface 2 a of theprotective layer 2 on which the lifespan-extending layer 3 is formed(the forming surface) has been smoothed, the forming surface ispreferably cleaned by means of a brush or air blowing etc. in order tocompletely remove dirt and foreign material.

The primer layer 4 is then formed by coating a primer on the cleanedsurface 2 a of the protective layer 2.

It should be noted that this mode of embodiment illustrates a case inwhich the primer layer 4 is provided, but this does not limit thepresent invention and it is equally possible to omit the primer layer 4if adhesion between the protective layer 2 and the lifespan-extendinglayer 3 is adequate by virtue of the surface state of the surface 2 a ofthe protective layer 2 etc.

A coating composition comprising the polymer compound constituting thecoating layer that forms the lifespan-extending layer 3 is then coatedon the surface 2 a of the protective layer 2 or on the surface 4 a ofthe primer layer 4, and said coating composition is cured in order toform the lifespan-extending layer 3.

The coating composition comprising the polymer compound that forms thetopcoat layer 5 is coated on the surface 3 a of the lifespan-extendinglayer 3, and said coating composition is cured in order to form thetopcoat layer 5, whereby construction is completed.

According to the method for slope face improvement of this mode ofembodiment, the coating layer having crack-following properties of 0.8mm or greater, salt-blocking properties and neutralization-preventingproperties is formed as the lifespan-extending layer 3 on the surface 2a of the protective layer 2 comprising mortar etc. sprayed on the slopeface 1 a of the foundation 1, and as a result it is possible to preventpenetration of rainwater and the like from cracks that form in theprotective layer 2, restrict degradation such as salt damage orneutralization of the protective layer, and also prevent detachment ofthe protective layer caused by the degradation. Furthermore, theresulting lifespan-extending layer 3 makes it possible to preventpenetration of rainwater etc. from cracks that form in the protectivelayer 2, and also has a punching strength of 0.3 kN or greater(Structure Construction Management (July 2015 edition, 3-6: Concrete,3-6-2: Surface Protection Requirement Performance, Nippon ExpresswayResearch Institute Company Limited)) which is able to prevent detachmentof the protective layer 2. Furthermore, the lifespan-extending layer 3has a large effect in terms of blocking salts such as calcium chlorideused as a snow-melting agent, so it is possible to prevent degradationof the protective layer 2 comprising mortar etc. caused by said salts.As a result, it is possible to prevent degradation of the protectivelayer 2 and detachmant of the mortar etc., and thus it is possible toenvision a longer lifespan for the protective layer 2.

Furthermore, according to the method for slope face improvement of thismode of embodiment, the different-colored region 6 is formed on thesurface 3 a of the lifespan-extending layer 3, and as a result it ispossible to provide a notification of information relating to theenvironment around the slope face 1 a (travel direction on the road 11running along the slope face 1 a, warning about a slope failure orlandslide etc.). Furthermore, by forming the lifespan-extending layer 3,the protective layer 2 comprising mortar etc. is not directly exposed towind and rain (snow and rain), so it is possible to prevent staining ofthe protective layer 2 and adhesion of contaminants, and therefore theesthetic appearance of the slope face 1 a can be maintained.

EXEMPLARY EMBODIMENT

The present invention will be described in more specific terms belowthrough an exemplary embodiment and comparative examples, but thepresent invention is not limited to the following exemplary embodiment.

Exemplary Embodiment

The surface of a protective layer comprising existing mortar that haddeteriorated was cleaned in order to remove dirt and foreign materialetc., after which a modified epoxy resin primer (commercial name:Resi-Primer PW-F, produced by Diflex) was applied over the protectivelayer in a coating amount of 0.2 kg/m², and a primer layer having athickness of 65 μm was formed.

A two-liquid ultra-fast-curing polyurethane resin (commercial name: CVSpray, produced by Diflex) was then applied by means of a spray gun overthe primer layer in a coating amount of 1.0 kg/m², and alifespan-extending layer having a thickness of 1000 μm was formed.

A two-liquid solvent-based acrylic urethane resin (commercial name:Resi-Top, produced by Diflex) was then applied by means of a spray gunover the lifespan-extending layer in a coating amount of 0.15 kg/m², anda topcoat layer having a thickness of 47 μm was formed.

The features of the method for slope face improvement according to theexemplary embodiment are shown in table 1.

Comparative Example 1

A protective layer comprising existing mortar that had deteriorated wasstripped away from a slope face on a foundation by human power and bymachine, after which mortar was sprayed on the slope face in the sameway as had been done with the existing protective layer in order to forma protective layer comprising mortar, whereby the slope face wasrepaired.

The features of the method for slope face improvement according toComparative Example 1 are shown in table 1.

Comparative Example 2

The surface of a protective layer comprising existing mortar that haddeteriorated was cleaned in order to remove dirt and foreign materialetc., after which a polymer cement (commercial name: Bask, produced byNichimaru Co.) was used to form a secondary protective layer comprisingthe polymer cement having a thickness of 2000 μm, whereby the slope facewas repaired.

The features of the method for slope face improvement according toComparative Example 2 are shown in table 1.

Comparative Example 3

Short fibers comprising steel fibers or organic fibers were disposed onthe surface of a protective layer comprising existing mortar that haddeteriorated, and mortar was sprayed in the same way as had been donewith the existing protective layer from above said short fibers in orderto form a protective layer comprising mortar, whereby the slope face wasrepaired.

The features of the method for slope face improvement according toComparative Example 3 are shown in table 1.

Exemplary Comparative Comparative Comparative Embodiment Example 1Example 2 Example 3 Cost Low High Low Medium Construction time Low HighLow Medium Useful life (years) 20 20 20 20 Performance Crack-followingHigh None Low None properties (1-10 mm) (0-0.5 mm) Salt-blocking HighNone Low None properties Water-blocking High Low Low Low propertiesNeutralization- High None Low None preventing properties Environment CO₂emission Low High because Low because High because amount because oftreatment small of large small and machinery machinery machinerytransportation was used used was used of waste material from removingexisting mortar etc. Noise Low High Low High Road Small- Large-scaleSmall-scale Large-scale restrictions scale traffic traffic restrictionsrestrictions because of because of heavy heavy machinery used machineryused Construction/ Management Few types Many types of Few types Manytypes Management of work work of work of work Construction Short LongShort Long period Ease of Simple Complex Simple Complex constructionEase of Possible Difficult Difficult Difficult construction (winterseason) Construction Small Large Small Medium restrictions

It is clear from table 1 that the lifespan-extending layer formed bymeans of the method for slope face improvement according to theexemplary embodiment on the surface of the protective layer comprisingexisting mortar that had deteriorated was superior in terms ofcrack-following properties, salt-blocking properties, water-blockingproperties and neutralization-preventing properties in comparison withthe protective layers formed by means of the slope face improvementmethods according to Comparative Examples 1-3 on the surface ofprotective layers comprising existing mortar that had deteriorated.Furthermore, the method for slope face improvement according to theexemplary embodiment not only made it possible to repair the slope facein a shorter construction period and at a lower cost than in the case ofthe methods for slope face improvement according to Comparative Examples1-3, the method according to the exemplary embodiment was also clearlysuperior from an environmental perspective in terms of lower carbondioxide emissions and less noise etc.

FIELD OF INDUSTRIAL APPLICATION

It is possible to improve safety and maintenance properties bysuppressing degradation of a protective layer on a cliff face or slopeface etc.

KEY TO SYMBOLS

-   1 . . . Foundation-   1 a . . . Slope face-   2 . . . Protective layer-   3 . . . Lifespan-extending layer-   4 . . . Primer layer-   5 . . . Topcoat layer-   6 . . . Different-colored region-   11 . . . Road

1. A method for slope face improvement, in which a lifespan-extendinglayer is layered on a surface of a protective layer comprising mortar orconcrete sprayed on a slope face, whereby penetration of rainwater fromcracks that form in the protective layer is prevented, degradation ofthe protective layer is restricted, and detachment of mortar pieces orconcrete pieces from the protective layer is prevented, wherein acoating layer having crack-following properties of 0.8 mm or greater,salt-blocking properties and neutralization-preventing properties isformed as the lifespan-extending layer.
 2. The method for slope faceimprovement as claimed in claim 1, wherein the coating layer comprises apolymer compound.
 3. The method for slope face improvement as claimed inclaim 1, wherein a primer layer is formed between the protective layerand the lifespan-extending layer.
 4. The method for slope faceimprovement as claimed in claim 1, wherein a topcoat layer is formed onthe lifespan-extending layer.
 5. The method for slope face improvementas claimed in claim 2, wherein the polymer compound is at least oneselected from the group consisting of: polyurethane resin, polyurearesin, epoxy resin and acrylic resin.
 6. The method for slope faceimprovement as claimed in claim 2, wherein a primer layer is formedbetween the protective layer and the lifespan-extending layer.
 7. Themethod for slope face improvement as claimed in claim 2, wherein atopcoat layer is formed on the lifespan-extending layer.
 8. The methodfor slope face improvement as claimed in claim 3, wherein a topcoatlayer is formed on the lifespan-extending layer.
 9. The method for slopeface improvement as claimed in claim 6, wherein a topcoat layer isformed on the lifespan-extending layer.
 10. The method for slope faceimprovement as claimed in claim 3, wherein the polymer compound is atleast one selected from the group consisting of: polyurethane resin,polyurea resin, epoxy resin and acrylic resin.
 11. The method for slopeface improvement as claimed in claim 6, wherein the polymer compound isat least one selected from the group consisting of: polyurethane resin,polyurea resin, epoxy resin and acrylic resin.
 12. The method for slopeface improvement as claimed in claim 4, wherein the polymer compound isat least one selected from the group consisting of: polyurethane resin,polyurea resin, epoxy resin and acrylic resin.
 13. The method for slopeface improvement as claimed in claim 7, wherein the polymer compound isat least one selected from the group consisting of: polyurethane resin,polyurea resin, epoxy resin and acrylic resin.
 14. The method for slopeface improvement as claimed in claim 8, wherein the polymer compound isat least one selected from the group consisting of: polyurethane resin,polyurea resin, epoxy resin and acrylic resin.
 15. The method for slopeface improvement as claimed in claim 9, wherein the polymer compound isat least one selected from the group consisting of: polyurethane resin,polyurea resin, epoxy resin and acrylic resin.